Wearable wireless sensing systems capable of monitoring critical biomarkers are increasingly valued for health monitoring and disease management. However, current systems often compromise on sensitivity, multi-parameter sensing capacity, compactness, power consumption, and wearing comfort, limiting their skin-interfaced applications. Here, we present a wireless, battery-free, multiplexed sensing system based on a high-order exceptional point (EP)—a singularity in non-Hermitian realm. This system features multiple distinct resonance frequencies that sensitively respond to physiological variations, exhibiting over 10-fold sensitivity improvement and 50% size reduction compared to conventional resonator-based systems. Moreover, the sensor employs a strain-resilient liquid metal composite and a soft substrate, ensuring wearing comfort, mechanical reliability, and antimicrobial properties. The effectiveness of this system is demonstrated through in situ monitoring of skin temperature and sweat electrolytes during exercise and prolonged monitoring of sweat glucose and ammonium in different subjects. The proposed system is highly transformative, offering benefits for various wearable applications.

Physically unclonable functions (PUFs) are a class of hardware-specific security primitives based on secret keys extracted from integrated circuits, which can protect important information against cyberattacks and reverse engineering. Here, we put forward an emerging type of PUF in the electromagnetic domain by virtue of the self-dual absorber-emitter singularity that uniquely exists in the non-Hermitian parity-time ( PT )–symmetric structures. At this self-dual singular point, the reconfigurable emissive and absorptive properties with order-of-magnitude differences in scattered power can respond sensitively to admittance or phase perturbations caused by, for example, manufacturing imperfectness. Consequently, the entropy sourced from inevitable manufacturing variations can be amplified, yielding excellent PUF security metrics in terms of randomness and uniqueness. We show that this electromagnetic PUF can be robust against machine learning–assisted attacks based on the Fourier regression and generative adversarial network. Moreover, the proposed PUF concept is wavelength-scalable in radio frequency, terahertz, infrared, and optical systems, paving a promising avenue toward applications of cryptography and encryption.

The requirement of multilevel cell (MLC) resistive random access memory (RRAM) for computing is different than that for MLC storage. It generally requires a linearly spaced conductance median and an ultratight conductance distribution, as the column current are summed up for analog computation. In this article, 3-bit per cell RRAM that is suitable for accurate inference of a deep neural network (DNN) is demonstrated, with ultratight conductance distribution (<1.5% sigma). First, a two-loop write–verify protocol is proposed. Then, statistical experiments are conducted on RRAM array fabricated in Winbond’s 90-nm process. By incorporating the measured conductance distribution into DNN simulation considering the real weight mapping, inference accuracy with only 0.5% degradation over software baseline is achieved for CIFAR-10 data set even when 128 rows are read-out in parallel. By enabling parallel read-out, the system-level energy efficiency and throughput could be improved by $5.3 \times $ and $4.4 \times $ , respectively, compared to the 3-bit per cell RRAM used as MLC storage.

Modern wireless implantable medical devices face escalating demand for lightweight and low-cost wireless solutions exploited to wake up sensors and transfer data. In this paper, we propose and experimentally demonstrate the efficient, multi-band wireless power transfer (WPT) systems that are symmetric with respect to the combined parity ( P ) and time reversal ( T ) transformations (i.e., space-time reflection symmetry). In analogy with non-Hermitian PT -symmetric physical systems that can have branching real eigenfrequencies as a function of the dimensionless non-Hermiticity and the coupling factor, the PT -symmetric WPT system exhibits multi-band and/or wideband operations via adjustment of the non-Hermiticity (i.e., quality-factor of resonant tanks) and their mutual inductive or capacitive coupling strength. Here, we put forward design and implementation for achieving dual-band, tri-band, and wideband PT -symmetric WPT systems, capable of operating in the industrial, scientific, and medical (ISM) bands (27.12 MHz and 40.68 MHz) with high transmission efficiency. This compact and low-cost WPT technique may be exploited in many practical applications, such as wireless charging of bioimplants and wearables, as well as interrogation of battery-free medical devices and internet-of-things (IoT) sensors to assist smart healthcare.